Precision M2800 - Hard drive removal

Hello,

I've been trying to upgrade the HDD in a Precision M2800 (according to the instructions here). The drive will not slide out, it's almost as if it's glued solid to the chassi, or I'm something very obvious. I've removed all screws as per instructions, and also remove the keyboard to see if there's any more screws that's not mentioned in the instructions. But the drive will not move.

The model in question has a 128GB SSD buitlin and I'm trying to replace it with a 512GB SSD. How much force do I need to remove the drive? I'm afraid I'll snap the plastic cover if I try with more force.